Chemical equilibrium controlled synthesis of polyoxymethylene dimethyl ethers over sulfated titania

The chemical equilibrium and reaction kinetic behavior in the synthesis of polyoxymethylene dimethyl ethers （DMMn） were investigated over sulfated titania in order to reveal the decisive factor controlling the reaction. The results showed that the molar ratio of adjacent DMMn products in equilibrium solution had the same value, which depended absolutely on the reaction temperature. Meanwhile, the reactions had the same DMMn products distributions under varied reaction conditions. The equilibrium constants of the related step-wise reactions for DMMn formation were equal, which were calculated based on the bulk compositions of the reaction solution. And thus, the selectivity to DMMn was mainly controlled by the chemical equilibrium, i.e., thermodynamic control. In brief, the present results provide some guidance for future synthesis of DMMn.

Selective hydrogenolysis of furfuryl alcohol to 1,5-and 1,2-pentanediol over Cu-LaCoO_3 catalysts with balanced Cu^O-CoO sites

Selective hydrogenolysis of biomass‐derived furfuryl alcohol(FFA)to 1,5‐and 1,2‐pentanediol(PeD)was conducted over Cu‐LaCoO3 catalysts with different Cu loadings;the catalysts were derived from perovskite structures prepared by a one‐step citrate complexing method.The catalytic performances of the Cu‐LaCoO3 catalysts were found to depend on the Cu loading and pretreatment conditions.The catalyst with 10 wt%Cu loading exhibited the best catalytic performance after prereduction in 5%H2‐95%N2,achieving a high FFA conversion of 100%and selectivity of 55.5%for 1,5‐pentanediol(40.3%)and 1,2‐pentanediol(15.2%)at 413 K and 6 MPa H2.This catalyst could be reused four times without a loss of FFA conversion but it resulted in a slight decrease in pentanediol selectivity.Correlation between the structural changes in the catalysts at different states and the simultaneous variation in the catalytic performance revealed that cooperative catalysis between Cu0 and CoO promoted the hydrogenolysis of FFA to PeDs,especially to 1,5‐PeD,while Co0 promoted the hydrogenation of FFA to tetrahydrofurfuryl alcohol(THFA).Therefore,it is suggested that a synergetic effect between balanced Cu0 and CoO sites plays a critical role in achieving a high yield of PeDs with a high 1,5‐/1,2‐pentanediol selectivity ratio during FFA hydrogenolysis.

Biosynthesis of poly-3-hydroxybutyrate with a high molecular weight by methanotroph from methane and methanol

Poly-3-hydroxybutyrate （PHB） can be produced by various species of bacteria. Among the possible carbon sources, both methane and methanol could be a suitable substrate for the production of PHB. Methane is cheap and plentiful not only as natural gas, but also as biogas. Methanol can also maintain methanotrophic activity in some conditions. The methanotrophic strain Methylosinus trichosporium IMV3011 can accumulate PHB with methane and methanol in a brief nonsterile process. Liquid methanol （0.1%） was added to improve the oxidization of methane. The studies were carried out using shake flasks. Cultivation was performed in two stages： a continuous growth phase and a PHB accumulation phase under the conditions short of essential nutrients （ammonium, nitrate, phosphorus, copper, iron （Ⅲ）, magnesium or ethylenediamine tetraacetate （EDTA）） in batch culture. It was found that the most suitable growth time for the cell is 144 h. Then an optimized culture condition for second stage was determined, in which the PHB concentration could be much increased to 0.6 g/L. In order to increase PHB content, citric acid was added as an inhibitor of tricarboxylic acid cycle （TCA）. It was found that citric acid is favorable for the PHB accumulation, and the PHB yield was increased to 40% （w/w） from the initial yield of 12% （w/w） after nutrient deficiency cultivation. The PHB produced is of very high quality with molecular weight up to 1.5 × 10^6Da.

Enantioselective epoxidation of olefins with hydrogen peroxide catalyzed by bioinspired aminopyridine manganese complexes derived from L-proline

Three chiral aminopyridine ligands derived from L-proline were prepared. Careful evaluation of the corresponding aminopyridine manganese complexes in asymmetric epoxidation of olefins revealed a broad substrate scope in the presence of 0.2 mol% manganese complex and 0.5 equiv. 2,2-dimethylbutyric acid, with aqueous hydrogen peroxide as an oxidant. A variety of olefins including styrenes, chromenes, and cinnamamides were transformed successfully into the target epoxides with moderate to excellent enantioselectivity（yield up to 95%, ee up to 99%）.

Intermediate formation enabled regioselective access to amide in the Pd-catalyzed reductive aminocarbonylation of olefin with nitroarene

An efficient route for the palladium-catalyzed reductive aminocarbonylation of olefins with nitroarenes was developed using carbon monoxide(CO)as both reductant and carbonyl source,which enables facile access to amides with excellent regioselectivity and broad substrate scope.It is found that the counter anions of the Pd catalyst precursors significantly affect the reaction chemoselectivity and amide regioselectivity.Branched amides were mainly obtained with K2PdCl4 as the metal catalyst,and phosphine ligands had no influence on the regioselectivity but affected the catalytic reactivity.However,phosphine ligands had significant effects on aminocarbonylation regioselectivity when Pd(CH3CN)4(OTf)2 was used;monodentate phosphines tended to form branched amides,and bidentate phosphines mainly formed linear amides.Trapping experiments,primary kinetic studies,and control reactions with all possible N-species reduced from nitroarene indicated that the catalytic synthesis of branched and linear amides produced nitrene(further converted to enamide)and aniline,respectively,different from the previous ligand-controlled regioselective synthesis of amides via the aminocarbonylation of olefins with amines.Furthermore,the proposed synthesis route could be applied in the synthesis of gram-scale propanil under mild conditions.

Effective synthesis of 5-amino-1-pentanol by reductive amination of biomass-derived 2-hydroxytetrahydropyran over supported Ni catalysts

A highly efficient and green process was developed for the synthesis of useful 5-amino-1-pentanol(5-AP)from biomass-derived dihydropyran by coupling the in situ generation of 5-hydroxypentanal(5-HP,via the ring-opening tautomerization of 2-hydroxytetrahydropyran(2-HTHP))and its reductive amination over supported Ni catalysts.The catalytic performances of the supported Ni catalysts on different oxides including SiO2,TiO2,ZrO2,γ-Al2 O3,and MgO as well as several commercial hydrogenation catalysts were investigated.The Ni/ZrO2 catalyst presented the highest 5-AP yield.The characterization results of the oxide-supported Ni catalysts showed that the Ni/ZrO2 catalyst possessed high reducibility and a high surface acid density,which lead to the enhanced activity and selectivity of the catalyst.The effect of reaction parameters on the catalytic performance of the Ni/ZrO2 catalyst was studied,and a high 5-AP yield of 90.8%was achieved in the reductive amination of 2-HTHP aqueous solution under mild conditions of 80℃and 2 MPa H2.The stability of the Ni/ZrO2 catalyst was studied using a continuous flow reactor,and only a slight decrease in the 5-AP yield was observed after a 90-h time-on-stream.Additionally,the reaction pathways for the reductive amination of 2-HTHP to synthesize 5-AP were proposed.

Cobalt carbonyl ionic liquids based on the 1,1,3,3-tetra-alkylguanidine cation:Novel, highly efficient, and reusable catalysts for the carbonylation of epoxides

A series of novel cobalt carbonyl ionic liquids based on1,1,3,3‐tetra‐alkyl‐guanidine,such as[1,1‐dimethyl‐3,3‐diethylguanidinium][Co(CO)4](3a),[1,1‐dimethyl‐3,3‐dibutylguanidinium][Co(CO)4](3b),[1,1‐dimethyl‐3,3‐tetramethyleneguanidinium][Co(CO)4](3c),and[1,1‐dimethyl‐3,3‐pentamethyleneguanidinium][Co(CO)4](3d),were synthesized in good yields and were also characterized using infrared spectroscopy,ultraviolet‐visible spectroscopy,1H nuclear magnetic resonance(NMR)spectroscopy,13C NMR spectroscopy,high‐resolution mass spectrometry,differential scanning calorimetry,and thermogravimetric analysis.The four compounds exhibited high thermal and chemical stability.In addition,the catalytic performance of these compounds was investigated in the carbonylation of epoxides,with3a exhibiting the best catalytic activity without the aid of a base as the additive.The catalyst could be reused at least six times without significant decreases of the selectivity or conversion rate.Moreover,the catalyst system exhibited good tolerance with terminal epoxides bearing alkyl,alkenyl,aryl,alkoxy,and chloromethyl functional groups.

NiCo/Al_(2)O_(3)nanocatalysts for the synthesis of 5-amino-1-pentanol and 1,5-pentanediol from biomass-derived 2-hydroxytetrahydropyran

Al_(2)O_(3)-supported monometallic Ni,Co,and bimetallic Ni-Co nanocatalysts originated from layered double hydroxide precursors were synthesized by co-precipitation method,and used for the synthesis of useful 5-amino-1-pentanol(5-AP)and 1,5-pentanediol(1,5-PD)by reductive amination(RA)or direct hydrogenation of biofurfuralderived 2-hydroxytetrahydropyran(2-HTHP),respectively.In both reactions,the yield of the target products decreased monotonously with the increasing amounts of Co in the NiCo/Al_(2)O_(3)catalysts,owing probably to the replacement of highly reactive Ni by Co component with inferior hydrogenation activity at the low reaction temperature of 60℃.However,the incorporation of Co could improve the reducibility of the NiCo/Al_(2)O_(3)bimetallic catalysts and promote the reaction stability of the catalysts,especially for Ni_(2)Co1/Al_(2)O_(3),in both reactions with over 180 h time-on-stream.Characterization of the catalysts before and after the reaction showed that the incorporating Co could inhibit the sintering of metal particles and hinder the surface oxidation of the more reactive Ni0species,thanks to the formation of Ni-Co alloy in the bimetallic catalysts.DFT-based modeling of the reaction mechanisms is also performed,supporting the reaction pathway proposed previously and also the much higher activity of Ni in the RA of 2-HTHP as compared with Co.

Natural attapulgite supported nano-Ni catalysts for the efficient reductive amination of biomass-derived aldehydes and ketones

The efficient synthesis of useful primary amines via reductive amination of biomass-based aldehydes and ketones over earth-abundant base metal catalysts is an attractive biomass value-adding technology yet facing lots of challenges.Herein,natural attapulgite(ATP)was applied as support for the fabrication of active Ni catalysts with different Ni loadings(5–30 wt%)by the deposition-precipitation method.The Ni/ATP-550 catalyst with 10–15 wt%Ni loadings was found to present the highest catalytic performance for the synthesis of valuable 5-amino-1-pentanol(5-AP)via reductive amination of biofurfural-derived 2-hydroxytetrahydropyran among a variety of commonly used oxide supports loaded Ni catalysts,as well as ATP supported nickel catalysts with other loadings,achieving 5-AP yield up to 94%.The intrinsic activity of the Ni/ATP catalysts was found to depend strongly on the Ni^(0) crystallite size and Ni^(0) fraction of the catalysts,which generally increased with increasing Ni^(0) crystallite size and fraction,owing probably to the hydrogenation of imine intermediate is a structure-sensitive reaction.The efficient 10Ni/ATP-550 catalyst also exhibited good activity and stability in the reductive amination of several other biomass-derived aldehydes and ketones to their corresponding primary amines with good to excellent yields(81%–99%).This work provided a clean and efficient natural ATP-supported non-noble metal nickel-based catalytic system for the reductive amination of aldehydes and ketones to synthesize high-value-added primary amines,which could be a promising candidate for the industrial production of amines.

手性Mn(Ⅲ)-Salen配合物催化的2-芳基环烷醇的高对映选择性氧化动力学拆分

本文发展了一种通过氧化动力学拆分获得光学活性2-芳基环烷醇的方法:该体系以N-溴代丁二酰亚胺为氧化剂,简单易得的手性Mn(Ⅲ)-salen配合物(0.5 mol%)为催化剂.该方法底物适用性广、具有高度的立体控制且易于进行克级规模的反应,为光学活性2-芳基环烷醇类化合物的合成提供了一种高效、实用的方法.

Versatile MOF-derived cobalt catalyst for the reductive amination

The tunable metal center and the tailorable organic linker of metal-organic framework(MOF)make the characteristic of ultrahigh porosity,controllable pore size,crystalline nature and highly-ordered structures[1].Since its emergence[2,3],it represents one of the most celebrated functional materials.Owing to the rich diversity of MOF family,a vast of important applications including the storage of gas,recognition of molecules as well as

Photoinduced Transition-Metal-Free Alkynylation of Alkyl Pinacol Boronates

An unprecedented visible-light-induced transitionmetal-free alkynylation of alkyl pinacol boronates has been demonstrated with alkynyl phenylsulfones as the alkynylation reagents and 4CzIPN as the organic photocatalyst.Common sodium methoxide(NaOMe)or sodium hydroxide(NaOH)was used as the Lewis base togeneratephotoactivetetra-coordinatedboron species.Various functional groupswerewell tolerated.The selective monoalkynylation of diboronates was achieved to keep one boryl group in the product for potential further transformations.Radical trapping experiments and electron paramagnetic resonance(EPR)analysis confirmed the generation of alkyl radical intermediate.

Bioinspired manganese complexes catalyzed epoxidation for the synthesis of the epoxyketone fragment of carfilzomib

We report herein an efficient catalytic epoxidation reaction for the synthesis of epoxyketone(tert-butyl((S)-4-methyl-1-((R)-2-methyloxiran-2-yl)-1-oxopentan-2-yl)carbamate), which is an important synthetic intermediate of carfilzomib. A series of bioinspired manganese complexes bearing N4 ligands are carefully investigated in the epoxidation of enone precursor with H_2O_2 as oxidant in the presence of carboxylic acid(e.g., acetic acid).

A novel manganese(Ⅲ)-peroxo complex bearing a proline-derived pentadentate aminobenzimidazole ligand

Manganese(Ⅲ)-peroxo complexes are invoked as key intermediates in the enzymatic cycles of Mncontaining enzymes, and the synthesis of reactive manganese(Ⅲ)-peroxo complexes with rationally designed ligand has been of great interest in the communities of bioinorganic and biomimetic chemistry.Herein, we designed a novel pentadentate aminobenzimidazole ligand and obtained its manganese(Ⅱ)complex, which was successfully applied in the synthesis of a reactive manganese(Ⅲ)-peroxo complex by treatment with hydrogen peroxide in the presence of triethylamine. The manganese(Ⅲ)-peroxo complex was well characterized with various spectroscopic techniques, including ultraviolet-visible(UV-vis)spectrophotometry, coldspray ionization time-of-flight mass spectrometry(CSI-TOF MS), and continuous wave electron paramagnetic resonance(CW-EPR) spectroscopy. Besides, its reactivity in aldehyde deformylation was investigated, demonstrating second-order kinetics in the reaction with 2-phenylpropionaldehyde and affording acetophenone as the sole product.